All,
Newbie here. So impressed with the knowledgeable people on this forum. Trying to decide on purchase of Philco 38-2 radio without speaker. Can anyone tell me if a replacement speaker from 38-4 would work in the 38-2? They are slightly different. The output Transformer Pri. for the 38-2 (H32) is 530. Output Transformer Pri. for the 38-4 (H29) is 660. How would using a speaker with a higher Output Trans. Pri. affect operation of the 38-2 radio? Appreciate any insights.
Thanks,
Michael
Admin note: Thread split to Philco Electronic Restoration
Hi,
There is a 38-2 speaker advertised on the auction site now.
https://www.ebay.com/itm/203934321227
Now let's examine the differences between the speakers.
Model 38-4 uses an H-29 speaker, the same as used in models 38-3 and 38-5.
Model 38-2 uses an H-32 speaker.
Both speakers have output transformers designed for use with push-pull 6F6G tubes.
Both have 660 ohm field coils.
I don't know why Philco lists a lower DC resistance for the output transformer primary on the 38-2 speaker when both are listed as having a primary impedance of 14,000 ohms.
It certainly looks like the H-29 and H-32 can substitute for one another.
Hi Michael and welcome to the Phorum. The output transformer is there to match the high impedance of the output tube to the low impedance of the speaker. You do this to get the best transfer of power with the least signal distortion. If the 38-4 has the same output tube then you are in luck, otherwise you'll have to make the comparison from the plate impedance specs of each tube. If they're close then you're OK with it. And this is assuming the speaker impedance is the same in either radio. The higher DC resistance of the 38-4 transformer will result in slightly lower plate voltage in the 38-2 output tube but if you temporarily connect it in the 38-2 you'll probably need to raise the volume a tad.
Really appreciate your insights. Will be checking out the 38-2 speaker on eBay. As an alternative, I feel pretty good about substituting 38-4. Thanks, Ron and RodB!
I think there is an error in the Philco Speakers information.
Models 38-2, 38-3, 38-4 and 38-5 speakers all use the same audio output transformer (32-7754). Therefore, they should all should have the same primary DC resistance.
With this in mind, I see no reason why you could not replace an H-32 with an H-29 and vice versa.
Thanks Ron. Purchased the 38-2 radio today and am working to obtain the correct speaker. Seller gave me a speaker, but he didn't know anything about it. He thought it was a Philco speaker; however, I haven't been able to identify it online yet. It is stamped 36-1552-4. it also has a 1-D-2284 stamp. I'm pretty sure it is not compatible, but I would like to ID it for future reference.
According to the parts list the speaker should be an H-32 , part no. 36-1299